The inside of the earth is very hot - hot enough to melt rocks. And the deeper you go the hotter it gets. Below the
surface the molten rock is called magma; at the earth's surface it becomes lava, although nothing has changed except
the name.The fresh magma is white hot, brillant enough that you would have trouble looking at it. But as it cools it
turns yellow, and then various shades of red. Eventually it cools enough to solidify completely and form an igneous
rock, such as the granite and basalt. Granite and basalt are the two most abundant igneous rocks at the earth's
surface.

Granite

Basalt

Magma/lava is a mixture of elements such as silica, iron, sodium, potassium, etc. As the magma/lava cools these elements
chemically combine, or crystallize, in geometric patterns to form
the eight rock forming minerals
(olivine, pyroxene, amphibole, biotite, orthoclase, muscovite, plagioclase and quartz).

For example, in the granite above the pink is orthoclase, the black biotite, and clear to gray mostly quartz.
These eight minerals form the bulk of igneous rocks. They are arranged in Bowen's Reaction Series (BRS) by
temperature of formation, high temperature ones at the top and low temperature ones at the bottom. Although
it is useful to know these minerals they are not essential for a basic understanding of igneous rocks.

Sedimentary Rocksare generally stratified, fine-grained
or composed of fragments of older rocks from which these
were derived, such as pebbles, sand, angular fragments of
older rocks, broken shells, rounded mineral grains and
alteration minerals such as clays. Limestones are easily
identified because they effervesce in dilute hydrochloric
acid. Many sedimentary rocks also contain fossils.

Metamorphic Rocksare sedimentary or igneous rocks that have
been altered by heat and/or pressure. As they are derived from previously
existing igneous, sedimentary or even metamorphic rock, their appearance is
variable. They are identified by the types of minerals they contain and their
texture. Thermally metamorphosed rocks occur bordering igneous intrusions, which
altered the surrounding rock originally because of their intense hear, resulting
also in the formation of new minerals such as andalusite and garnet. Regionally
metamorphosed rocks occur in the roots of mountain ranges, where intense
pressures and high temperatures formed platy minerals (e.g. mica) and
high-pressure minerals (e.g. staurolite).

Minerals and rocks are stable
only under the conditions at which they form. Change the conditions and
the rocks will change to adapt to the new conditions.

Metamorphism occurs when any previously existing rock, the parent rock,
is buried in the earth under layers of other rock. The deeper the rock
is buried the hotter it gets, and the higher the pressure becomes.
Eventually, rock must adjust to the new conditions, whether it is
baked, or squeezed, or both, and in the process becomes a metamorphic
rock.

Various transformations are included in the rock cycle which says all rocks can be transformed into other rocks (rock cycle discussion)
as environmental conditions change When metamorphism runs its entire
course a sedimentary rock is baked into a metamorphic rock, and
eventually melted into an igneous rock.

The earth is an open system, and it dissipates energy. The energy comes from the Earth's molten interior, and has kept it tectonically active for 4.5 billion years, and will probably continue for another 4-5 billion years into the future when, finally, the heat supply will run out, and the earth will die. Of course, by that time the sun will enter into its red giant phase and the Earth will be burned to a crisp anyway.
But it is this energy from the interior that has driven the Earth's physical/chemical evolution, and been ultimately responsible for all the rocks, continents, mountains, foreland basins, etc. Without it the earth would be like the moon or Mars, geologically dead and in equilibrium.
All of these rock and tectonic features on Earth reflect the underlying principle not only of geology but the universe: "minerals and rocks are stable only under the conditions at which they form; change the conditions and the rocks change too."

Almost all of the rock that we have on Earth today is made of the same
stuff as the rocks that dinosaurs and other ancient life forms walked,
crawled or swam over. While the stuff that rocks are made from has stayed
the same, the rocks themselves, have not. Over time rocks are recycled
into other rocks. Moving tectonic
plates are responsible for destroying and forming many different types
of rocks.

Soil by volume, on the average consists of 45%
mineral, 25% water, 25% air
and 5% organic matter (both living and dead organisms).
There are thousands of different soils throughout the world.

Five important factors influences the specific soil that develops.

Parent Material

Minerals and organic materials present during it's formation. Materials from
volcanos, sediment transported by wind, water or glaciers or minerals left
behind by drying lakes are good examples of parent materials.

Climate

Parent material is broken down into smaller pieces by a process called
weathering. Cycles of freezing and thawing, wetting and drying, and the
frequency of these occurrences coupled with average temperature and moisture
levels of region play an important role in soil formation. These smaller
pieces are known as (sand, silt and clay), clay being the smallest size.

Living Organisms

Both plants and animals help to create a soil. As they die, organic matter
incorporates with the weathered parent material and becomes part of the
soil. Living
animals such as moles, earthworms, bacteria, fungi and nematodes
are all busy moving through or digesting food found in the soil. All of
these actions mix and enrich the soil.

Topography

Topography is the hilliness, flatness, or amount of slope of the land. Soils
vary with topography primarily because of the influence of moisture and
erosion. In many areas, moist, poorly drained soils are located in low
areas, and depressions of the land. In contract, soils in sloping areas can
be drier and well drained. These soils tend to be moderately and well
developed. Erosion can remove all or part of the topsoil and subsoil,
leaving weakly developed soil.

Time

It may take hundreds of years to form one inch of soil from parent material.
Only the top few inches are productive in the sense of being able to sustain
plant growth. This is why soil
conservation is so important.

The result of all of these forces is soil that develops
into layers known as horizons. The first or top 48
inches of these horizons and its' unique set of characteristic is used by soil
scientist to classify and name a soil. Just as an oak tree is named due to its'
unique characteristics, so is a soil.

These horizons collectively are known as a soil
profile. The thickness varies with location, and under disturbed conditions:
heavy agriculture, building sites or severe erosion for example, not all
horizons will be present.

The uppermost is called the organic
horizon or O horizon. It consists of detritus, leaf litter and other organic
material lying on the surface of the soil. This layer is dark because of the
decomposition that is occurring. This layer is not present in cultivated fields.

Below is the A horizon or topsoil. Usually it is darker than
lower layers, loose and crumbly with varying amounts of organic matter. In
cultivated fields the plowed layer is topsoil. This is generally the most
productive layer of the soil. This is the layer that soil
conservation efforts are focused.

As water moves down through the topsoil, many soluble minerals
and nutrients dissolve. The dissolved materials leach downward into lower
horizons.

The next layer is the B horizon or subsoil. Subsoils are
usually lighter in color, dense and low in organic matter. Most of the materials
leached from the A horizon stops in this zone.

Still deeper is the C horizon. It is a transition area between
soil and parent material. Partially disintegrated parent material and mineral
particles may be found in this horizon.

At some point the C horizon will give up to the final horizon,
bedrock.

Texture class is one
of the first things determined when a soil is examined. It is related
to weathering and parent material. The differences in horizons may be
due to the differences in texture of their respective parent
materials.

Texture class can be
determined fairly well in the field by feeling the sand particles and
estimating silt and clay content by flexibility and stickiness. There
is no field mechanical-analysis procedure that is as accurate as the fingers
of an experienced scientist, especially if standard samples are
available. A person must be familiar with the composition of the local
soils. This is because certain characteristics of soils can create
incorrect results if the person does not take these characteristics into
account.

In some environments
clay aggregates form that are so strongly cemented together that they feel
like fine sand or silt. In humid climates iron oxide is the
cement. In desert climates silica is the cement and in arid regions
lime can be the cement. It takes prolonged rubbing to show that they
are clays and not silt loams.

Some soils derived
from granite contain grains that resemble mica but are softer. Rubbing
breaks down these grains and reveals that they are clay. These grains
resist dispersion and field and laboratory determinations may
disagree.

Many soil conditions
and components mentions earlier cause inconsistencies between field texture
estimates and standard laboratory data. These are, but not limited to,
the presence of cements, large clay crystals, and mineral grains. If
field and laboratory determinations are inconsistent, one or more of these
conditions is suspected.

The organic soil component contains
all the living creatures in the soil and the dead ones in various stages of
decomposition. An acre of living soil can contain 900 pounds of earthworms, 2400
pounds of fungi, 1500 pounds of bacteria, 133 pounds of protozoa, 890 pounds of
arthropods and algae, and even small mammals in some cases. In fact, the soil
could be viewed as a living entity, rather than an inert body.

The soil's organic matter also contains dead organisms, plant matter and
other organic materials in various phases of decomposition. Humus, the
dark-colored organic material in the final stages of decomposition, is
relatively stable. Both organic matter and humus serve as a reservoir of plant
nutrients; they also help to build soil structure and provide other benefits.

The type of healthy living soil required to support humans now and far into
the future will be balanced in nutrients and high in humus with a high diversity
of soil organisms. It will produce healthy plants with minimal weed, disease and
insect pressure. To accomplish this we work with the natural processes
and optimize their functions to sustain our farms.

In
1975, Soil Taxonomy was published by the United States Department of
Agriculture's Soil Survey Staff. This system for classifying soils has
undergone numerous changes since that time, and the 2nd edition was
published in 1999. Soil Taxonomy remains one of the most widely used
soil classification systems in the world.

Click on each soil order for a high-resolution, printable PDF file.
For a high resolution PDF version of the entire poster, click on the title
in the center of the poster. (All of these links are also listed
below.)

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